A reflective plate is used in various situations in order to utilize light efficiently. Recently, a light source has been changed to a semiconductor-based one, that is a semiconductor laser, a light-emitting diode (hereinafter referred to as LED) or the like, because of downsizing an apparatus and a light source. Therefore, the reflective plate is surface-mounted on a printed-circuit board or the like, and required to have not only mechanical strength, but also good heat resistance and precision moldability. The reflective plate is also required to have stable high reflectance for a long time and in particular, to suppress decreasing the reflectance of a reflective material due to heating in the steps of assembling LED and reflow soldering.
Furthermore, a cost reduction of products using a reflective plate has been remarkably required, recently. And also it is required: to decrease the number of LED packages mounted on an end product such as TV, a monitor and so on to increase the luminance of an LED element; to downsize a product; to increase the number of the LED packages by injection molding; and the like. Therefore, a reflective material preferably has high molding processability and is particularly required to have high melt-flowability. In addition, a reflective material is being required to improve the strength and the toughness hand in hand with the downsizing of a product.
Glass fibers are generally used in wide applications as a reinforcing material of a reflective plate. However, the melt-flowability of a reflective material would be low for a large number of molded articles by one shot, and the molded articles would have a gate-cut surface with roughness, and particularly in a small-sized product, the gate-cut surface with roughness tends to significantly affect a product appearance.
Various improvements have been attempted in order to solve this problem. There are inorganic reinforcing materials, for example Wollastonite (PTL 1), potassium titanate (PTL 2), and a combination of potassium titanate and titanium oxide (PTL 3).
However, by blending a multiple kinds of the reinforcing materials, there is concern about decreasing the reflectance and the mechanical strength because of a poor dispersion of the reinforcing materials in a base polymer. Furthermore, a special screw configuration, temperature setting, and the like would be required for good dispersion of reinforcing materials in a base polymer in the melt mixing. There is a possibility of decreasing properties due to the decomposition thereof by increasing a load to base polymers, and a cost would increase.
On the other hand, a technique of suppressing decreasing the reflectance of a reflective plate by improving a base polymer is also shown (PTL 4). In many examples, a polyamide material is used for a reflective plate, however discoloration derived from a terminal amino group or an amide bond would occur, resulting in decreasing the reflectance. Therefore, a heat-resistant polyester is attempted to be used instead of a polyamide resin. However, there are no reports how the mechanical strength and the flowability would be changed by alternating a polyamide and a heat-resistant polyester, and the performance balance of a reflective material is unknown.
Further, PTL 4 discloses a method in which a composition containing a heat-resistant polyester and a polymer containing a glycidyl methacrylate group is used for increasing strength and toughness.